Process for the prevention of selective corrosion of tubes and machinery parts of copper or copper containing alloys



F. VON WURSTEMBERGER. PROCESS FOR THE PREVENTION OF SELECTIVE CORROSION 0F TUBES AND MACHINERY PARTS OF COPPER 0Rv COPPER CONTAINING ALLOYS.

APPLICATION FILED JUNE 7, 1919.

1,335,209, Patented Mar. 30, 1920,

; impellers and tube sets of copper and copperwhich are in contact with UNITED sT TEs PATENT curios.

FRANZ vou wuas'ramaaacna, or zuarcn, swrrzaammn, ASSIGNOB. T0 AKTIEN- GESELLSGHAFT DER MASGHINENFABRIKEN ESCI-IER WYSS 65 cm, or .zumcn,

SWITZERLAND.

I PROCESS FOR THE PREVENTION OF SELECTIVE CORROSION 0F TUBES AND MACHINERY PARTS OF COPPER 0B COPPER CONTAINING ALLOYS.

To all whom it may concerrt:

Be it known that I, FRANZ VON WURSTEM- BERGER, a citizen of the Republic of Switzerland, residing at Hardturmstrasse 19, Zurich, Switzerland, have invented certain new and useful Improvements in Processes for the Prevention of Selective Corrosion of Tubes and Machinery Parts of Copper or Copper Containing Alloys; and I do hereby declare the following to be a clear, full, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same, reference being had to the accompan ing drawing, and to letters or figures 0 reference marked thereon, which form a part of this specification.

The invention consists of a process for the prevention of selective corrosion of tubes and machinery parts. of copper or copper containing alloys which are in contact with water containlng 1011s for instance water containing chlorids and of contrivances used for the employment of the process. Selective corrosion is understood to be that phenomenon whereby fluids which, according to their chemical composition, will at tack one portion of metallic parts immersed therein, or in contact therewith, and not other portions. i

This phenomenon, known as pitting, occurs, for instance, on anodes of copper immersed in sodium salt solutions Na CO' under the influence of electrolysis, or on aluminium anodes in .chlorid solutions, for instance, NaCl or MgCl In practice it is known as the cause of destruction of pump containing alloys sea water or with water which conducts electricity, owing to the presence of any'kind of salt which itcontains in solution.

- Careful investigations have shown that" the cause of selective corrosion is entirely due to the alteration of the surface of the metallic parts. in question and not to the metal not being homogeneous, and that the phenomenon is due toelectrolytically difler' I ent qualities which the different areas acuire under the influence of certain deposits;

such slightly soluble salts of the metals,

in question come into consideration and actransformation Specification of Letters ratent. Patented Mar. 30, 1920. Application filed June 7, 1919. Serial No.- S02,627.

cordingly selective corrosion does not occur and physical naturewhich are dependent on the nature of the metal in question as also on the salts contained in the water.

One quality which water producing selective corrosion must possess at any rate is a certain electric conductivity. It does not follow however that all water conducting electricity produces selective corrosion.

, The behavior of copper and copper containing alloys in contact with water which possess a certain electric conductivity owing to the presence of certain chemicals is' briefly explained as follows:

Two different areas of a piece of metal immersed in the water are to be considered as two electrodes in short circuit through the metal itself. At first as soon as the piece of metal is immersed a dilference of potential usually arises between the two areas, which diflerence is dependent on the nature of the layer with which the surfaces of the two areas are covered under the action of oxidation in the air before immersion. The layer on both areas. Under the influence of this difference of potential one area becomes an anode the other a cathode. However this difference of potential disappears quickly as the electric current produced by it, roduces salts on the anode area, through w v ich the concentration of creased. v

The galvanic element formedby the two areas'is polarized in this way. By such local electrolysis the whole metal surface is brought in a short time to an equal potential which is higher than the: potential of a bright, newly immersed piece of the same metal. i

A continuous attack on any spot is only anodicdepolarizadepolarization malty possible 'where constant tion takes place. Such occur through mechanical erosion of metallic ions there is'inposited anodic products or through chemical of those products into slightly soluble compounds, under chemical influence which is equivalent to a reduction which the two electrodesthemse a The drawing shows. schematicall a device; '60

Figures l and 2 show a device which canbe-used 1n an open channel leading water to of the concentratien of metal i us on this spot. The polarizing layer whic is found on copper in water containing chlorid consists "of protochlorid of copper CuGl 5 and basic chlorids of various structure into protoxid of copper, further compounds 10 of all sorts having an alkaline reaction, which transform the CuCl into Cu(OH), hydrate of protoxid. f

The character of the attack due to such a depolarization depends on the nature of the deposit with alka ine reaction, for instance hydroxid of magnesium deposited in solid form will produce a distinctly'iimited area of attack accordin to its slight solubility. On the contrary the easily soluble caust1c soda solution NaOI-I will act as. depolarizer as far as it can spread by diffusion.

As polarizers, z. e, chemicals favorin equalization of potential or preventing loca be essential.

ever is not practicable because of its secondary action of destroying metals.

On the contrary, an addition of easily acid reaction as chlorid of aluminium AlCl and rotochlorid of iron FeCl as well as chlorid of iron FeCl, were found to be good.

According to the process in question for the prevention ofselective corrosion on maparts of copper or copper contam-' chine ing al oys am easily soluble hydrolytically decomposing salt of acid reaction is added to the water. Such a salt might also be produced immediately in the water which 1s to be made innocuous, as anode product by sending an electric current through the" -,water and using a suitable metallic anode. The cathodic products are to be carriedaway. v

A. contrivance suitable for the employmerit of the process consists of two electrodes through w h1ch an electric current is made to pass and is so arranged that the cathodicproducts are carried away.-

between electrodes and walls the plpmgs surrounding the electrodes are to be built of electrically nonconducting material, as for instancecay.-

than .double "the tension of for earrying outjmymethod w th ferric .a surface condensin plant.- Fi .1 shows ,the longitudinal section 'throught e channel attack I have found an addition of acid to Direct addition of acidfhowa carried awalyl' soluble hydrolytically decomposing salts of.

I To avoid injurious secondary electrolysis For-the same purpose the electric tensions .employed may 'bekept low' at an "rate less o arization, ves p.

. acid reacting s and the single parts of'the device. -Fig'.' 2 shows the cross/section on II-II.

The cooling'water is supplied to the con denser 1' (the copper or brass cooling pipes of which must be rotected from selective corrosion or pitting by means of a centrif- 'ugal pump 2 from an open channelin which which is made of any conducting material,

say of iron, is surrounded by a clay pipe. An electric .current is supplied from an source 6- (for instance from a generator through both electrodes. The clay pipe 7 which rests on the supports 10, is. open' underneath toward the channel and is provided .with a discharge .pipe'B, which keeps the water level in the pi e somewhat lower than the water level -in t e channel, so that the products of electrolysis, such as soda solu tion NaOH and other hydroxids as also hy drogen which form at the cathode 5, are continually carried awa rid (FeCl,) forms at the anode 4, and is by the stream of water, as shown by t e dotted arrows 9 in Fig. 1. Ferric -protochlorid is transformed partly into a basic chlorid by the air in the water and partly into ferric chlorid, and acts asa preventive of corrosion, both on the bronze wheel of thepump 2 as also on the copper cooling tubes in the condenser 1, p

The 'anode4 should be arranged in such a manner that the strongest electrolytic ac- The dottedv arrows 14 show the path of the.

electric current from the anode 4 to the cathode 5. The intensit "of the current must vary according to t e; uantity' of injurious salts. cYmtained'in t e water,and will be adjusted toa minimum by suitably choosing the tension and determin'ng the distance. between the anode 4 and 'ecathode 5.

I Apparatus other than that shown herein forms the subject matter of my application Ser'. No. 303,406, filed July 11, 1919.

I claim 1. The process fonthe prevention of selec tiv'e corrosion of tubes and machinery parts of copper or copper containing alloys, .which are in contact with water containing ions, consist" in introducing into theflj water an easily] so uble as preventive means. 2. The process for the prevention of selectivecorrosion of tubes and machinery parts l of copper or copper containing alloys, which are in contact with water containing ions consisting of introducing-into the water by lilydrolytically decomposable t I e 125 Iron protochlotion takes place at the oint. (13) farthest 12) in order, that.

electrolytic action within the water an easily soluble hydrolytically decomposable acid reacting salt. I

3. The process for the prevention of selective corrosion of tubes and machinery parts of copper or copper containing alloys, whlch are in contact with water containing ions,

consisting of the electrolytic production in the corrosive water with which the machinery parts are in contact, of an easily soluble hydrolytically decomposable acid reactingsalt as anodic product, the cathodic product being carried away.

4. The process for the prevention of selective corrosion of tubes and machinery parts of copper or coppercontaining alloys, which are-in contact with water containin ions, consistin of the employment of ferric chlo- 1 as preventive means.

5. The process for the prevention of selective corrosion of tubes and machineryparts of copper or copper containing alloys that are in contact with water containing ions,

comprising the electrolytic production of a 'hlorid of iron as anode product in the corrosive water with which the machinery parts come in contact, the cathode product being carried away.

6. The process for the prevention of selective corrosion or pitting of water-contact' ing machinery parts containing copper or 

